Microelectronic devices (e.g. dies) are typically manufactured in large number on a semiconductor wafer. For various reasons, the devices may fail to perform correctly. Accordingly, as a part of the manufacturing process, various tests of the microelectronic devices are typically performed. Tests can include, for example, functional tests, speed tests and sorting, and burn-in testing. Testing can be performed at the wafer level (e.g., before the microelectronic devices are separated from each other in a process called singulation) to allow failed to devices to be identified before packaging the devices.
To perform tests on the microelectronic devices, temporary electrical connections to the devices are made. For example, a wafer can be placed into a prober, and the wafer placed onto a movable stage. The stage can be moved to bring the wafer into contact with a probe card assembly. The probe card assembly can include many probes that are arranged to make temporary pressure-based electrical contacts to corresponding terminals (e.g., aluminum bond pads) on the microelectronic devices. Alignment of the wafer and probe card assembly can be performed using optical systems. Testing can involve sending signals to and from the wafer through the probes.
Because of the small sizes of the terminals and probes, it is challenging to ensure and maintain proper alignment between the probe card assembly and the wafer. Typically, the probe card assembly is mounted (e.g., bolted or otherwise fixed in position) into the prober to maintain a fixed position of the probe card assembly relative to the stage. Various adjustment mechanisms can be provided in the prober, probe card assembly, or both to allow alignment operations (e.g., tilt adjust) to be performed to place the tips of the probes into parallel alignment with the surface of the stage (and thus, into alignment with terminals of the wafer).
Maintaining proper alignment can be complicated when temperature variations are present, as most materials change dimension as a function of temperature. It is often advantageous to test the microelectronic devices over a range of temperatures. To this end, heating or cooling elements can be included in the stage or other portions of the prober to heat or cool the microelectronic devices during testing. Moreover, even if heating or cooling elements are not included, operation of the microelectronic devices during testing may generate heat. The resultant heating or cooling can cause the wafer, probe card assembly, and the prober to expand or contract, changing the positions of the probes relative to the terminals. For example, differential changes in the dimension of the probe card assembly relative to the mounting structure (e.g., cardholder) of the prober to which the probe card assembly is mounted can cause bowing or bending of the probe card assembly. If the bowing is toward the stage, one or more of the probes may press against the electronic devices with too much force and damage the devices or the probes. Conversely, if the bowing is away from the stage, one or more of the probes may fail to make reliable electrical contact with the terminals of the electronic devices, resulting in erroneous test results.